MicroRNA-218 increases cellular sensitivity to Rapamycin via targeting Rictor in cervical cancer

The roles of microRNA in human cervical cancer

Although a potentially preventable disease, cervical cancer (CC) is the second most commonly diagnosed gynaecological cancer with at least 530,000 new cases annually, and the prognosis with CC is still poor. Studies suggest that aberrant expression of microRNA (miRNA) contributes to the progression of CC. As a group of small non-coding RNA with 18-25 nucleotides, miRNA regulate about one-third of all human genes. They function by repressing translation or inducing mRNA cleavage or degradation, including genes involved in diverse and important cellular processes, including cell cycling, proliferation, differentiation, and apoptosis. Results showed that misexpression of miRNA is closely related to the onset and progression of CC. This review will provide an overview of the function of miRNA in CC and the mechanisms involved in cervical carcinogenesis.

Emerging roles of microRNAs in regulating the mTOR signaling pathway during tumorigenesis

The mammalian target of rapamycin (mTOR) is a large Ser/Thr protein kinase that belongs to the phosphoinositide 3-kinase (PI3K) family and mediates various physiological and pathological processes, especially cell proliferation, protein synthesis, autophagy, and cancer development. The mTOR expression is transient and tightly regulated in normal cells, but it is overactivated in cancer cells. Recently, several studies have indicated that microRNAs (miRNAs) play a critical role in the regulation of mTOR and mTOR-associated processes, some acting as inhibitors and the others as activators. Although it is still in infancy, the strategy of combining both miRNAs and mTOR inhibitors might provide an approach to selectively sensitizing tumor cells to chemotherapy-induced DNA damage and subsequently attenuating the tumor cell growth and apoptosis.

[MicroRNA-152 and microRNA-448 inhibit proliferation of colorectal cancer cells in vitro by targeting Rictor]

OBJECTIVE

To screen the microRNAs (miRNAs) targeting Rictor and investigate their effects in regulating the biological behaviors of colorectal cancer (CRC).

METHODS

Human colorectal cancer cell line KM12SM was transfected with the miRNAs targeting Rictor identified by prediction software to test inhibitory effects of these miRNAs on Rictor expression using qRT-PCR and Western blotting. Dual luciferase reporter assay was used to further confirm the binding of these miRNAs to the 3'UTR of Rictor mRNA. Cell survival and colony formation assays were used to investigate the effects of these miRNAs on survival and colony formation in KM12SM cells.

RESULTS

miR-152 and miR-448 were identified as the Rictor-targeting miRNAs, which significantly inhibited the expression of Rictor in KM12SM cells (P < 0.05). The two miRNAs were confirmed to bind to the 3'UTR of Rictor mRNA and significantly inhibited luciferase activity in KM12SM cells (P < 0.01, P < 0.05); they also showed activities of posttranscriptional modulation of Rictor. Overexpression of miR-152 and miR-448 both significantly inhibited the growth and colony formation of KM12SM cells.

CONCLUSIONS

miR-152 and miR-448 can down-regulate the protein expression of Rictor by targeting Rictor mRNA to negatively regulate the growth and colony formation of colorectal cancer cells.

Retraction Statement: 'MicroRNA-218 increases cellular sensitivity to Rapamycin via targeting Rictor in cervical cancer' by Li J, Wang J, Wang Y, Qiu H

The above article from APMIS, published online on 24 April 2015 in Wiley Online Library (wileyonlinelibrary.com) and in Volume 123, pp. 562-570, has been retracted by agreement between the authors, the journal Editors in Chief, Professors Bodil Norrild, Ben Vainer and Elisabeth Ralfkiaer, and John Wiley & Sons Ltd. The article has been retracted due to errors in the reported results. In this study, the authors used HeLa and SiHa cell lines to investigate the biological roles of miR-218. However, subsequently it emerged that the two cell lines were contaminated in the laboratory by other unknown cell lines. When repeating the experiments, it was found that the functions of miR-218 were not as significant as had been previously reported, especially its effects on rapamycin sensitivity. Reference Li J, Li X, Wang J, Wang Y, Qiu H. MicroRNA-218 increases cellular sensitivity to Rapamycin via targeting Rictor in cervical cancer. APMIS 2015; 123:562-570. doi: 10.1111/apm.12387.

Human adipose mesenchymal stem cell-derived exosomal-miRNAs are critical factors for inducing anti-proliferation signalling to A2780 and SKOV-3 ovarian cancer cells

An enigmatic question exists concerning the pro- or anti-cancer status of mesenchymal stem cells (MSCs). Despite growing interest, this question remains unanswered, and the debate became intensified with new evidences backing each side. Here, we showed that human adipose MSC (hAMSC)-derived conditioned medium (CM) exhibited inhibitory effects on A2780 human ovarian cancer cells by blocking the cell cycle, and activating mitochondria-mediated apoptosis signalling. Explicitly, we demonstrated that exosomes, an important biological component of hAMSC-CM, could restrain proliferation, wound-repair and colony formation ability of A2780 and SKOV-3 cancer cells. Furthermore, hAMSC-CM-derived exosomes induced apoptosis signalling by upregulating different pro-apoptotic signalling molecules, such as BAX, CASP9, and CASP3, as well as downregulating the anti-apoptotic protein BCL2. More specifically, cancer cells exhibited reduced viability following fresh or protease-digested exosome treatment; however, treatment with RNase-digested exosomes could not inhibit the proliferation of cancer cells. Additionally, sequencing of exosomal RNAs revealed a rich population of microRNAs (miRNAs), which exhibit anti-cancer activities by targeting different molecules associated with cancer survival. Our findings indicated that exosomal miRNAs are important players involved in the inhibitory influence of hAMSC-CM towards ovarian cancer cells. Therefore, we believe that these comprehensive results will provide advances concerning ovarian cancer research and treatment.

Deregulated miRNAs in human cervical cancer: functional importance and potential clinical use

Cervical cancer (CC) is one of the most common malignancies affecting women worldwide. While the morbidity and mortality associated with CC are decreasing in western countries, they both remain high in developing countries. Unfortunately, many issues about molecular mechanisms of CC are not clear yet. miRNAs are a group of small noncoding RNAs that could post-transcriptionally modulate the expression of specific genes and participate in the initiation and progression of multiple diseases including CC. In the last decade, mounting evidences suggest an association between miRNAs and human papillomavirus infection, as well as variations in biologic behavior, treatment response and prognosis in CC. Herein, we highlight the latest findings in this area and the potential applications.

Inactivation of fatty acid synthase impairs hepatocarcinogenesis driven by AKT in mice and humans

BACKGROUND & AIMS

Cumulating evidence underlines the crucial role of aberrant lipogenesis in human hepatocellular carcinoma (HCC). Here, we investigated the oncogenic potential of fatty acid synthase (FASN), the master regulator of de novo lipogenesis, in the mouse liver.

METHODS

FASN was overexpressed in the mouse liver, either alone or in combination with activated N-Ras, c-Met, or SCD1, via hydrodynamic injection. Activated AKT was overexpressed via hydrodynamic injection in livers of conditional FASN or Rictor knockout mice. FASN was suppressed in human hepatoma cell lines via specific small interfering RNA.

RESULTS

Overexpression of FASN, either alone or in combination with other genes associated with hepatocarcinogenesis, did not induce histological liver alterations. In contrast, genetic ablation of FASN resulted in the complete inhibition of hepatocarcinogenesis in AKT-overexpressing mice. In human HCC cell lines, FASN inactivation led to a decline in cell proliferation and a rise in apoptosis, which were paralleled by a decrease in the levels of phosphorylated/activated AKT, an event controlled by the mammalian target of rapamycin complex 2 (mTORC2). Downregulation of AKT phosphorylation/activation following FASN inactivation was associated with a strong inhibition of rapamycin-insensitive companion of mTOR (Rictor), the major component of mTORC2, at post-transcriptional level. Finally, genetic ablation of Rictor impaired AKT-driven hepatocarcinogenesis in mice.

CONCLUSIONS

FASN is not oncogenic per se in the mouse liver, but is necessary for AKT-driven hepatocarcinogenesis. Pharmacological blockade of FASN might be highly useful in the treatment of human HCC characterized by activation of the AKT pathway.